The rapid growth in the use of the Internet and the World Wide Web ("the Web") has sparked a dramatic increase in the development of Internet-based software applications. Developments in Internet software have arisen in many different areas ranging from on-line shopping and banking to games and entertainment. Web-based tools such as Java, JavaBeans, and ActiveX have helped to partially bridge the gap between the simple, text-only Web pages of the early Internet and sophisticated software applications. In particular, these tools allow Web designers to include small, special-purpose programs (sometimes referred to as "applets", "Beans", or more generally, "components") within Web pages written in a hypertext language, such as the Hypertext Mark-up Language (HTML). Thus, Web pages have been transformed from passive, text-only displayable documents to dynamic documents that can provide moving graphics, video, sounds, and interactive capability.
While progress is being made in the development of Internet applications, application development tools for the Internet still have a number of shortcomings. For example, conventional Web-oriented programming models such as Java, JavaBeans, and ActiveX are not "tier-neutral" with respect to the environments in which they run. That is, the services upon which such models rely tend to be very specific to the tier (e.g., client or server), operating system, and in some cases, hardware. For example, while Java and JavaBeans do not have operating system and hardware dependencies as ActiveX controls do, they must exist in an environment or infrastructure that provides the necessary services (e.g., communications, access to environment, parameterization, connectivity to external services, etc.) to operate.
The surrounding environment or infrastructure in prior art application development systems tend to be tier-specific. The tools, mechanisms, and services available on client tiers, for example, are quite different from those available on server tiers. In heterogeneous hardware environments, the server tiers may also provide significantly different environments. Further, these systems do not allow components of an application to be moved from one tier to another, or to be distributed among multiple tiers. Such capability may be desirable for purposes of performance, security, or browser capability.
In addition, with conventional tools, interfaces between applets or other executable components must be custom-coded into the hypertext document. In particular, an application developer specifically "wires" (i.e., writes code for) the connections between components, so that the components can communicate with each other. This constraint makes it difficult for inexperienced programmers to create Web applications and causes application development to be a laborious, time consuming process.
A common approach to creating application development tools for the Web has been to retrofit existing tools with Web "front ends" (user interfaces). As a result, such tools are not ideally-suited to the development of Web applications. Further, retrofitted tools are not likely to adapt well to future changes in the platforms, users, and types of usage of the Internet.
Hence, it would be desirable to have Internet applications and application development mechanisms which overcome the above-mentioned disadvantages. In particular, what is needed is an application development mechanism that is specifically designed for development of Internet applications, especially Web-based applications. What is further needed is a single development mechanism that is based on a single, tier-neutral model, using which application developers can create application components for execution on any tier on a network, distribute application components across multiple tiers on a network, or move application components from tier to tier. In addition, what is needed is an application development mechanism which allows Internet applications to be created faster and more easily by people who have little or no programming experience.